Various components are provided into a well to complete the well. Such components include casing, tubing strings, control lines, sensors, control devices, valves, packers, mandrels and so forth. Once such components are installed, a perforating operation is typically performed to extend perforations through tubings and/or casing and into the surrounding formation. The perforations enable the communication of fluids between the surrounding formation and the wellbore.
To perform a perforating operation, a perforating gun is lowered into the well to a target depth. However, prior to firing the perforating gun, a well operator has to first ensure that the perforating gun will not fire in a direction that would destroy downhole components such as control lines, sensors, control devices, tubing strings, and so forth. Conventionally, various orientation techniques have been employed to identify a direction of perforation for the perforating gun that would not destroy downhole components.
One technique that has been employed is to use detection tools that emit an electromagnetic field and that can detect distortion in the magnetic field induced by a target component (such as a tubing string, control line, sensor, a mass positioned at a predetermined location, and so forth). The distortion can be used to determine the location of the target component. However, if a ferromagnetic layer (such as the layer of a steel casing or steel tubing) is provided between the target component and the detector tool, or beyond the target component and the detector tool, then the ferromagnetic layer can potentially interfere with accurate detection of the location of the target component based on detecting distortion caused by the target component.
The inability to accurately detect the location of a downhole component may result in destruction of the component if a perforating gun is inadvertently fired in the direction of such component. Usually, it is quite expensive to replace the destroyed component, since completion hardware must be removed from a well to perform replacement or repair operations.